Save an Extra 15% on Select Sale Items »

Niner S.I.R. 9 Mountain Bike Frame - 2016

Compiling options for this bike.
It'll be just a moment...

Item # NNR0030

Find your size

Note: Actual inseam is not the same as pant inseam.  How to measure

We recommend a size in this bike.

Edit More details

Our size calculator is a starting point for finding the right size for you. To get personal advice talk to one of our fit experts at 1.877.550.2639 or chat now

Select options
  • Select options
  • Blaze Yellow, L ($999.00)
  • Blaze Yellow, M ($999.00)
  • Blaze Yellow, S ($999.00)
  • Blaze Yellow, XL ($999.00)
  • Arctic White, S ($999.00)
  • Arctic White, M ($999.00)
  • Arctic White, L ($999.00)
  • Arctic White, XL ($999.00)
Compiling options for this bike.
  • 100% Guaranteed Returns
Item # NNR0030

Selected Option:

Add to cart save for later
Customer Service Represintative
Need help?

Ask an expert.

  • 1.888.276.7130
  • Live chat

Steel will always be real.

Aside from an occasional oddball, like magnesium or something from the kingdom Plantae, material choices for mountain bike frames are aluminum, steel, and carbon fiber. Each one has distinct advantages and disadvantages, and the amount of time that's been spent deviling into their nuances is unfathomable. But, based on common deductions, there are solid reasons why Niner would continue to offer an updated S.I.R. 9 among its carbon and aluminum 29ers.

The S.I.R. 9, along with the alloy AIR 9, launched Niner into mountain biking's limelight. And it's hard to believe that the S.I.R. 9 is already approaching eight revolutions of the big yellow orb since it began humiliating bouncy bikes with lesser wheels. In that time, we've seen carbon eclipse ferrous and aluminum chassis due to gram counters' love affair with fibers and epoxy. But, steel still holds its own when it comes to ride quality and value.

Most manufacturers pick either aluminum or steel for a price-point line. Niner chose to use both -- alloy for its entry level line, while reserving steel for the seasoned rider who can appreciate its distinct ride characteristics, and who doesn't need to drain a bank account on a carbon rig to chase KOM's. If you're not up to speed on the differences between steel and aluminum, the quick and dirty is that aluminum is intently stiffer and lighter, so it tends to accelerate quicker, but it can be more fatiguing due to vibration -- imaging holding onto a jackhammer all day. Steel, on the other hand, dampens trail chatter and has a natural spring-like nature that results in lively and encouraging handling on singletrack. In this case, Niner uses proprietary Reynolds 853 tubing with custom S-bend rear seatstays and chainstays. The tubing's wall thicknesses, including the down tube and top tube, are tweaked both externally and internally to produce the best possible ride quality for each frame size.

Clean TIG welds provide the strength, while short chainstays and a steep head angle offer the maneuverability that tight, twisty trails require. Niner also gave the S.I.R. 9 a radically sloping top tube for plenty of stand-over clearance in all its sizes. From the beefy tire clearance to the down tube shaped to avoid interference with fork crowns, everything about this frame shows the design time invested. And because of this extensive R & D, and willingness to use new standards and technology that benefit 29ers, Niner's developed a reputation for being ahead of the curve. Good luck trying to find another steel frame that has 142mm rear spacing, a post mount rear caliper, and the option to run just about any drivetrain configuration out there -- from single speed to multi-speed.

The S.I.R. 9 features Niner’s exclusive Bio-Centric EBB technology. An essential design element of the Bio-Centric system is that the cups lock to the bottom bracket shell’s flange. Once the EBB is in position, one bolt tightens the eccentric to the flanges, providing 360 degrees of purchase, while eliminating any chance for creak-causing dirt or debris to contaminate the interface. Also, because forces are no longer placed against the inside of the shell, it won’t round out or suffer from the over-tightening issues of traditional EBB designs.

This simple solution makes the S.I.R. 9 the true Zen-machine that SS bikes should be. The wheel can be removed without hassling with the caliper position or chain tension, and you’re guaranteed perfect dropout-to-frame alignment -- unlike individually adjustable sliding drops. All that you need to do to set up the S.I.R. 9 for gears is to add the derailleur hanger dropout and swap the EBB for one of Niner's CYA press fit adapters.

If you plan on going the geared route, Niner recommends doubles not exceeding 26/39 chainrings for SRAM, and 28/40 for Shimano. However, a standard triple will pose no problems. The rear triangle will accommodate a 2.4in tire, and you can run a 160mm rear rotor. You’ll need a bottom pull, high mount front derailleur with a 28.6mm clamp. The S.I.R. 9 uses a 27.2mm seatpost, a 73mm BB (only external style bottom brackets work with the EBB), and a 44mm tapered headset. The maximum chainring size varies depending on the position of the BioCentric EBB insert. At the most rearward position, the Niner recommends running no larger than a 30t chainring, and when in the forward position, it will accept a 36t ring. It comes with a Maxle rear axle.

The Niner S.I.R. 9 Mountain Bike Frame is available in the colors Arctic White and Tamale Red and in four sizes from Small to X-Large.

  • Reynolds 853 steel frameset
  • 142mm rear spacing
  • Eccentric bottom bracket

Tech Specs

Frame Material:
Head Tube Diameter:
[upper cup] ZS44/28.6, [lower cup] EC44/40
Headset Included:
Bottom Bracket Type:
Niner Bio-Centric EBB
Cable Routing:
Front Derailleur Mount:
28.6mm clamp-on, high-clamp
Derailleur Pull:
Compatible Components:
Shimano, SRAM
Seatpost Diameter:
27.2 mm
Recommended Use:
cross country
Manufacturer Warranty:
2 years on frame

sizing chart

SIR 9 size by rider height


Geometry chart

Fuji Bicycles


Geometry Chart


Altamira LTD

Seat Tube


Effective Top Tube








Head Tube


Head Tube Angle


Seat Tube Angle


Bottom Bracket Drop


Chainstay Length



44 44.0cm 51.5cm


36.3cm 72.1cm


72.0 deg 75.0 deg 6.9cm 40.5cm 97.1cm
47 47.0cm 53.0cm


37.0cm 74.1cm 13.0cm 72.5 deg 74.5 deg 6.9cm 40.5cm 97.7cm
50 50.0cm 54.5cm 54.0cm 37.0cm 76.0cm 14.0cm 73.0 deg 73.5 deg 6.9cm 40.5cm 97.6cm
53 53.0cm 56.0cm 56.0cm 37.9cm 78.3cm 16.0cm 73.5 deg 73.5 deg 6.9cm 40.5cm 98.6cm
55 55.0cm 57.5cm 58.0cm 38.9cm 80.1cm 18.0cm 73.5 deg 73.5 deg 6.9cm 40.5cm 100.1cm
58 58.0cm 59.0cm 60.1cm 39.7cm 82.1cm 20.0cm 74.0 deg 73.5 deg 6.9cm 40.5cm


Reviews & Community


Write a review

    Add a:
  • Photos
  • Videos

No file chosen

Rather attach a photo from your computer?


Only jpg, jpeg, png, gif or bmp files please.

Submit ReviewCancel

Here's what others have to say...


Very happy with this frame

  • Familiarity:I've used it several times

I built the frame up XT 1x11 and easton wheels, coming in at around 21 pounds total for a large. I am really pleased with the way this rides, and it's trustworthy steel! The attention to detail is obvious in the welds and workmanship. If you want a lightweight but modern steel frame this is one of the few that checks all of the boxes. I am also really happy that Competitive Cyclist pays attention to detail before shipping their frames. They do prep work like reaming and facing the head tube, etc. Saves time and money on your build.

Very happy with this frame

WIll my S Roval 142 wheel set fit? It uses a Syntace axle not a Shimano. Thanks.

If the rear end is a 12x142 it will fit. You will just need to use the axle that comes with the Niner frame as the treads in the frame are different.


Modern-technology be damned, sometimes

  • Gender:Male
  • Familiarity:I've used it several times

I've loved the idea of a steel bike since the beginning. There are (literally) millions of threads and blog postings talking about why steel is still a relevant (and good) material to use for bike frames, so I won't delve into all of that. I came off a Pivot LES, and a Highball Carbon before that, so I've had my fair share of creme de la creme carbon hardtails. To feed my never-ending lust for steel, I decided to give the new SIR9 a try. The stereotypes are true - it's pretty heavy, it is really smooth (smoother in the rear than either of my previous carbon hardtails), and is relatively heavy (yep, it's like a pound or two heavier than my other frames were). But for me, especially this time of year, I don't really care all that much. I don't have to worry about damaging the frame (I suppose I need to be conscious of rusting, but FrameSaver should take care of that), and it's pretty inexpensive. And it's fun, and different. And it's easy to make it single speed or geared. I dig it - when spring rolls around and I go back to slogging up thousands of feet of vertical, my tune my change a bit, but as a cool all-around hardtail (especially for midwest riding), this thing is rad.

Modern-technology be damned, sometimes